Synthetic grafts are rarely used as venous substitutes because of high rates of occlusion. The purpose of this study is to determine the extent to which patency of venous grafts is affected by 1) endothelial cell seeding, 2) antiplatelet therapy, 3) fibronectin used as a coating factor for endothelial cells. Endothelial cell seeding (ECS) is the process by which harvested endothelial cells are implanted onto the inner surface of a prosthetic graft to provide a lesser thrombogenic surface. This proposal calls for the use of ECS (single stage, 2 or 7 day-cultured cells) to cover the inner surface of prosthetic grafts implanted in vena cava of dogs (GI, II, III). Antiplatelet agent (ASA) will be added to ECS in GIV and V to prevent early graft thrombosis. Fibronectin will be added to the above regimen with the expectation that it will increase the "take" of seeded cells (GVI). Vena cavograms will be taken on days 3 and 7 after graft insertion to evaluate for patency. Grafts will be removed four weeks after implantation and evaluated for 1) patency, 2) thrombus free surface area, 3) surface area covered by seeded cells. It is expected that the combination of ECS, antiplatelet agent and fibronectin will yield the highest patency rate. A positive result calls for future studies on 1) various types of grafts, 2) production of prostaglandin or thromboxane by seeded cells, 3) amount of cells required for seeding. A negative result will call for more studies on factors which may affect venous grafts 1) low flow state, 2) formation of intimal hyperplasia, 3) types of grafts.